Outboard marine engines tend to exhibit rapid and often premature deterioration due to water corrosion. Most engine blocks employ aluminum cylinder castings, which are surrounded and otherwise bounded by a water jacket. These castings are highly susceptible to corrosion, particularly when the engine is used in a saltwater environment where electrolysis is likely to occur. Such corrosion is accelerated if the boat owner neglects to flush the engine after each use.
Progressive corrosion of the engine block often leads to total failure of the engine. The cylinder castings and the cylinder head are sealably interengaged by a conventional head gasket. Excessive pitting and corrosion of the castings will eventually cause the head gasket to fail. As a result, cooling water from the water jacket leaks into one or more of the combustion chambers and the engine malfunctions.
Traditionally, corroded engine blocks have been discarded and replaced. This is expensive and highly inefficient. The only known technique that attempts to repair the engine block involves the replacement of the cast iron cylinder sleeve. This sleeve, which is surrounded by the casting, is removed and replaced by an entirely new sleeve having a circumferential flange. This procedure is almost as expensive and inefficient as replacing the entire engine block. Considerable time, expense and complexity are required to manufacture these special replacement sleeves.